1. Field of the Invention
The invention relates to a hydraulic emergency control for a continuously variable transmission.
2. Prior Art
In German Patent Application DE 195 19 162.5, which had not been published by the filing date of the present application, a hydraulic emergency control for an electronically controlled continuously variable transmission (CVT) is described. The CVT that is preferably used in passenger cars has a control unit for emergency operation that assures tension of the transfer means by simple hydraulic means if the electrohydraulic triggering for normal driving operation should fail. These simple hydraulic means are described in conjunction with FIG. 1.
They assure on the one hand startup at full load, for instance, without slippage of the transfer means, and on the other after startup assure gear shifting from a high startup gear ratio to a low overdrive ratio.
The hydraulic valves, which switch over from the normal driving mode to the emergency operation mode, are held in the normal driving mode in the switching and/or control positions necessary for this driving mode with the aid of electromagnetic actuators.